android4.4組件分析--service組件-bindService源碼分析，android4大組件

android4.4組件分析--service組件-bindService源碼分析，android4大組件
6.1.1.    bindService

    因為有前面分析startService的代碼實現過程，則對於bindService的程式碼分析就不用那麼詳細介紹，在介紹流程的同時更關注一些細節上的部分。

 

首先，bindService也是通過 ContextWrapper.bindService，再到ContextImpl的bindService，然後是bindServiceCommon，需要注意的是，傳入的ServiceConnection被轉換成IServiceConnection類型，

    private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,

            UserHandle user) {

        IServiceConnection sd;

…

            sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),

                    mMainThread.getHandler(), flags);

…

            int res = ActivityManagerNative.getDefault().bindService(

                mMainThread.getApplicationThread(), getActivityToken(),

                service, service.resolveTypeIfNeeded(getContentResolver()),

                sd, flags, user.getIdentifier());

}

 

接下去是進入AMS的bindService，再調用ActiveServices.java 的bindServiceLocked，它會把IServiceConnection執行個體存放到ConnectionRecord裡面，並執行bringUpServiceLocked，

    int bindServiceLocked(IApplicationThread caller, IBinder token,

            Intent service, String resolvedType,

            IServiceConnection connection, int flags, int userId) {

…

            ConnectionRecord c = new ConnectionRecord(b, activity,

                    connection, flags, clientLabel, clientIntent);

 

            IBinder binder = connection.asBinder();

 

            if ((flags&Context.BIND_AUTO_CREATE) != 0) {

                s.lastActivity = SystemClock.uptimeMillis();

                if (bringUpServiceLocked(s, service.getFlags(), callerFg, false) != null){

                    return 0;

                }

            }

…

            if (s.app != null && b.intent.received) {

                // Service is already running, so we can immediately

                // publish the connection.

                try {

                    c.conn.connected(s.name, b.intent.binder);

                } catch (Exception e) {

                    Slog.w(TAG, "Failure sending service " + s.shortName

                            + " to connection " + c.conn.asBinder()

                            + " (in " + c.binding.client.processName + ")", e);

                }

 

                // If this is the first app connected back to this binding,

                // and the service had previously asked to be told when

                // rebound, then do so.

                if (b.intent.apps.size() == 1 && b.intent.doRebind) {

                    requestServiceBindingLocked(s, b.intent, callerFg, true);

                }

            } else if (!b.intent.requested) {

                requestServiceBindingLocked(s, b.intent, callerFg, false);

            }

}

 

 

根據之前的分析ServiceLocked會調用realStartServiceLocked，而realStartServiceLocked則先調用scheduleCreateService，完成service的建立和Oncreate（）的執行，然後執行requestServiceBindingsLocked，這個是bind服務相關處理，最後是sendServiceArgsLocked，這個是Start服務的處理。

    private final void realStartServiceLocked(ServiceRecord r,

            ProcessRecord app, boolean execInFg) throws RemoteException {

…

            app.thread.scheduleCreateService(r, r.serviceInfo,                    mAm.compatibilityInfoForPackageLocked(r.serviceInfo.applicationInfo),                 app.repProcState);

…

        requestServiceBindingsLocked(r, execInFg);

       sendServiceArgsLocked(r, execInFg, true);

…

}

 

 

requestServiceBindingsLocked再調用ActivityThread的方法scheduleBindService，在ActivityThread.java 中，它發出一個BIND_SERVICE事件，被handleBindService處理，

    private void handleBindService(BindServiceData data) {

…

                    if (!data.rebind) {

                        IBinder binder = s.onBind(data.intent);

                        ActivityManagerNative.getDefault().publishService(

                                data.token, data.intent, binder);

                    } else {

                        s.onRebind(data.intent);

                        ActivityManagerNative.getDefault().serviceDoneExecuting(

                                data.token, 0, 0, 0);

                    }

…

這裡先調用服務的onBind方法，因為服務是重載的，所以會執行具體服務類的方法，並返回服務裡的binder執行個體，這個binder隨後會被使用到，

其中AMS的publishService方法被調用，在 ActivityManagerService.java中又會調用   ActiveServices.java 的publishServiceLocked，

    void publishServiceLocked(ServiceRecord r, Intent intent, IBinder service) {

…

                    for (int conni=r.connections.size()-1; conni>=0; conni--) {

                        ArrayList<ConnectionRecord> clist = r.connections.valueAt(conni);

                        for (int i=0; i<clist.size(); i++) {

                            ConnectionRecord c = clist.get(i);

…

                            try {

                                c.conn.connected(r.name, service);

                             } …

 

                serviceDoneExecutingLocked(r, mDestroyingServices.contains(r), false);

這裡主要調用到c.conn.connected，c就是ConnectionRecord，其成員conn是一個IServiceConnection類型執行個體，這在前面有提到，connected則是其實作類別的方法。

 

對於IServiceConnection，它是一個介面，位置在(frameworks\base): core/java/android/app/IServiceConnection.aidl，aidl定義如下，它只有一個介面方法connected，

oneway interface IServiceConnection {

    void connected(in ComponentName name, IBinder service);

}

 

其服務端的實現在LoadedApk.java，如下，InnerConnection類是在ServiceDispatcher的內部類，並在ServiceDispatcher的建構函式裡面執行個體化的，其方法connected也是調用的ServiceDispatcher的方法connected，

        private static class InnerConnection extendsIServiceConnection.Stub {

            final WeakReference<LoadedApk.ServiceDispatcher> mDispatcher;

 

            InnerConnection(LoadedApk.ServiceDispatcher sd) {

                mDispatcher = new WeakReference<LoadedApk.ServiceDispatcher>(sd);

            }

 

            public void connected(ComponentName name, IBinder service) throws RemoteException {

                LoadedApk.ServiceDispatcher sd = mDispatcher.get();

                if (sd != null) {

                    sd.connected(name, service);

                }

            }

        }

 

        ServiceDispatcher(ServiceConnection conn,

                Context context, Handler activityThread, int flags) {

            mIServiceConnection = new InnerConnection(this);

            mConnection = conn;

            mContext = context;

            mActivityThread = activityThread;

            mLocation = new ServiceConnectionLeaked(null);

            mLocation.fillInStackTrace();

            mFlags = flags;

        }

 

這裡就再回到我們前面的ContextImpl裡面bindServiceCommon方法裡面，這裡進行ServiceConnection轉化為IServiceConnection時，調用了mPackageInfo.getServiceDispatcher，mPackageInfo就是一個LoadedApk執行個體，

    /*package*/ LoadedApk mPackageInfo;

 

    private boolean bindServiceCommon(Intent service, ServiceConnection conn, int flags,

            UserHandle user) {

        IServiceConnection sd;

 

            sd = mPackageInfo.getServiceDispatcher(conn, getOuterContext(),

                    mMainThread.getHandler(), flags);

}

 

所以，getServiceDispatcher會建立一個ServiceDispatcher執行個體，並將ServiceDispatcher執行個體和ServiceConnection執行個體形成KV對，並在ServiceDispatcher的建構函式裡將ServiceConnection執行個體c賦值給ServiceConnection的成員變數mConnection，

    public final IServiceConnection getServiceDispatcher(ServiceConnection c,

            Context context, Handler handler, int flags) {

        synchronized (mServices) {

            LoadedApk.ServiceDispatcher sd = null;

            ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher> map = mServices.get(context);

            if (map != null) {

                sd = map.get(c);

            }

            if (sd == null) {

                sd = new ServiceDispatcher(c, context, handler, flags);

                if (map == null) {

                    map = new ArrayMap<ServiceConnection, LoadedApk.ServiceDispatcher>();

                    mServices.put(context, map);

                }

                map.put(c, sd);

…

}

 

 

這樣，在執行ServiceDispatcher的connected方法時，就會調用到ServiceConnection的

onServiceConnected，完成綁定ServiceConnection的觸發。

        public void doConnected(ComponentName name, IBinder service) {

…

            if (old != null) {

                mConnection.onServiceDisconnected(name);

            }

            // If there is a new service, it is now connected.

            if (service != null) {

                mConnection.onServiceConnected(name, service);

            }

}

 

至此，就執行完了bindService的主要過程。

 

我們下面用一張圖來總結這個流程，

android中的service與開啟service的組件是否處於同一線程？

同一個進程，但是不是同一個線程，看你的樣子應該知道進程和線程的區別，但是仍然不建議做修改
 
android 中的採用bindService()啟動服務，為何沒有調用onServiceConnected（）方法，

你這個寫的太奇葩了，我第一次看見這樣寫的。難道不應該有一個extends Service的class麼，我還真是第一次看見用Activity來實現serviceConnection的，都不好評價你這個到底是對是錯